Gregory Scott Griffin

First Results from the Submillimeter Polarimeter for Antarctic Remote Observations: Evidence of Large-Scale Toroidal Magnetic Fields in the Galactic Center

We have observed the linear polarization of 450 μm continuum emission from the Galactic center, using a new polarimetric detector system that is operated on a 2 m telescope at the South Pole. The resulting polarization map extends ~170 pc along the Galactic plane and ~30 pc in Galactic latitude, and thus covers a significant fraction of the central molecular zone. Our map shows that this region is permeated by large-scale toroidal magnetic fields. We consider our results together with radio observations that show evidence of poloidal fields in the Galactic center and with Faraday rotation observations. We compare all of these observations with the predictions of a magnetodynamic model for the Galactic center that was proposed in order to explain the Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude that the observations are fundamentally consistent with the model.We have observed the linear polarization of 450 µm continuum emission from the Galactic center, using a new polarimetric detector system that is operated on a 2 m telescope at the South Pole. The resulting polarization map extends � 170 pc along the Galactic plane and � 30 pc in Galactic latitude, and thus covers a significant fraction of the central molecular zone. Our map shows that this region is permeated by large-scale toroidal magnetic fields. We consider our results together with radio observations that show evidence for poloidal fields in the Galactic center, and with Faraday rotation observations. We compare all of these observations with the predictions of a magnetodynamic model for the Galactic center that was proposed in order to explain the Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude that the observations are basically consistent with the model.

Anisotropy in the cosmic microwave background at degree angular scales: Python V results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37 to 45 GHz in two frequency bands. With a 091 × 102 beam, the instrument fully sampled 598 deg2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise, but has a sharply increasing slope starting at l ~ 150.

First results from viper: Detection of small scale anisotropy at 40 GHZ

Results of a search for small-scale anisotropy in the cosmic microwave background (CMB) are presented. Observations were made at the South Pole using the Viper telescope, with a 0&fdg;26 (FWHM) beam and a passband centered at 40 GHz. Anisotropy band-power measurements in bands spanning the range of l in which the first acoustic peak is expected (bands centered at l=108, 173, 237, 263, 422, and 589) are reported. Statistically significant CMB anisotropy is detected in all bands.

Using White Dish CMB Anisotropy Data to Probe Open and Flat-Λ CDM Cosmogonies

We use data from the White Dish experiment to set limits on cosmic microwave background radiation anisotropies in open and spatially flat-Λ cold dark matter cosmogonies. We account for the White Dish calibration uncertainty and marginalize over the offset and gradient removed from the data. Our 2 σ upper limits on the amplitude of the cosmic microwave background radiation anisotropy are larger than those derived previously. These upper limits are consistent with those derived from the COBE Differential Microwave Radiometer data for all models tested.

Early results from SPARO: Instrument characterization and polarimetry of NGC 6334

The Submillimeter Polarimeter for Antarctic Remote Observations (SPARO) employs two nine-element arrays of 3He-cooled bolometers to measure linear polarization at λ = 450 μm. It is operated at the focal plane of the Viper telescope, located at the Amundsen-Scott South Pole Station. SPARO obtains better sensitivity to degree-scale polarized submillimeter emission than can be currently achieved with any other experiment. We describe the design of SPAROs optics, detectors, and electronics. We also review the design of the SPARO cryostat, which has already been discussed in a previous paper. We discuss the performance of SPARO and Viper during observations at the South Pole in 2000, and we present polarimetric observations of NGC 6334 made with SPARO. Finally, we compare these observations with submillimeter polarimetric observations of the same source made at the Caltech Submillimeter Observatory and the James Clerk Maxwell Telescope, and we discuss the implications of these three data sets for the magnetic field in NGC 6334.